This invention is generally in the field of electric lamp assemblies, and particularly in that of socket structures for mechanical and electrical engagement with bulbs. More particularly, the invention pertains to a waterproof socket construction for use on motor vehicles or the like.
Automotive lamp assemblies have been known and used extensively wherein the bulb is removably mounted to a lamp body via a socket structure. Being wholly or nearly exposed to the atmosphere, the socket structure for automotive use must be impervious to water.
A typical conventional lamp socket construction for automotive use comprises a molded plastic body having a hollow extending axially therethrough, with the diameter of the hollow being reduced in two steps to provide two annular shoulders disposed adjacent the rear end of the socket body and directed forwardly thereof. Snugly received in the larger diameter portion of the hollow is a tubular, metal ferrule having its rear end bent inwardly and further rearwardly for abutting engagement with the internal annular shoulders of the socket body. The ferrule has mounted therein an insulating disk carrying a foot contact electrically connected to a cable extending rearwardly therefrom through a rubber packing closing the rear end of the socket body. This packing has a flange on its front end to engage the inwardly bent rear end portion of the ferrule, a tapered rear end portion protruding rearwardly of the socket body, and an annular groove intermediate its axial ends for receiving the rearwardly bent portion of the ferrule.
According to this prior art socket construction, the rubber packing is in direct engagement with the metal ferrule. The packing requires the annular groove for engagement with the ferrule, while the latter must have its rear end portion bent inwardly and further rearwardly for engagement with the packing. Consequently, the fabrication of both rubber packing and metal ferrule requires complex equipment. During the assemblage of the socket, too, the proper interengagement of the packing and ferrule necessitates a troublesome and time consuming procedure, adding to the manufacturing cost of the socket.
As an additional shortcoming of the noted conventional socket construction, the ferrule which forms part of a path for electric current has its rear end portion protruding into the reduced diameter portion of the hollow in the socket body and so is not sufficiently protected from water by the packing. Still further, being mostly engaged with the ferrule, the packing has made rather poor watertight contact with the socket body. These weaknesses have so far been compensated for by applying a sealant such as that of a hotmelt composition to the rear end of the socket body so as to seal its joint with the packing. This conventional solution is of course unsatisfactory because of the additional step of assemblage required. The packing itself has so far served little purpose for waterproofing the socket; rather, it has added to its manufacturing cost.